Military veterans returning from Afghanistan and Iraq with troubled mental health may also suffer the burden of more medical illnesses, according to a sweeping study.

Female veterans in particular seem hard hit by the one-two combination of post-traumatic stress disorder (PTSD) and additional medical conditions, such as headaches and lower-back disorders.

The most hard-hit veterans represented a relatively small group out of the 90,000 men and women who used the U.S. Veterans Health Administration (VHA) services. The study compared veterans with and without PTSD who had just returned from military service in Operation Enduring Freedom (Afghanistan) and Operation Iraqi Freedom.

Study researcher Susan Frayne, a physician with VA Palo Alto Health Care System and Stanford University, cautioned that the researchers could only point to an association between the PTSD and additional medical illnesses. Only future studies may answer whether PTSD somehow directly contributes to the additional conditions.

Grim statistics

The study found 3,501 female veterans with PTSD out of 12,831 total returning from Afghanistan and Iraq (and who accessed VHA services), along with 27,083 male veterans with PTSD out of 77,727 total returning home.

Such figures do not include veterans with other stress-related disorders or other mental health conditions.

Overall, the study found 222 types of medical conditions in veterans. Of the female veterans, 32 percent of the PTSD sufferers had “high numbers of medical conditions,” or 10 or more diagnosed ailments, as opposed to just 11 percent of those with no mental health conditions.

About 20 percent of the male veterans with PTSD had high numbers of medical conditions, compared with 7 percent among those who had no mental health conditions.

"Unfortunately we do not know whether the condition(s) started before military service," Frayne told LiveScience. "We also do not know whether the condition was related to military service or unrelated to military service."

Unknown causes

The researchers offer several possibilities for why the small group of PTSD sufferers tended to have from more medical conditions. PTSD itself may somehow increase the risk of medical illness – though that has yet to be proven.

"One way this could happen is that PTSD can cause changes in the neuroendocrine system in the body, which might affect other biological processes," Frayne explained.

PTSD could also have associations with certain health behaviors that can negatively affect physical health, such as smoking or alcohol use.

Another possibility is that whatever trauma led to PTSD also triggered the other medical conditions. A roadside bomb explosion might expose a veteran to broken bones or brain injury, as well as cause the emotional trauma related to PTSD.

Then there's the possibility that physicians simply pay more attention to PTSD patients and are more likely to record a medical diagnosis for them, as opposed to a patient with no mental health condition. For instance, PTSD patients might require more frequent visits that allow more chances for physicians to diagnose other conditions.

But Frayne's group still found PTSD patients suffered a higher burden of medical illness, even after taking into account frequent of primary care visits.

"There may be differences in the kinds of trauma they experience; for example, rates of sexual trauma are higher in women than in men, and that type of trauma might affect health differently than does trauma from combat or from a motor vehicle accident," Frayne pointed out.

The military roles that men and women each play may also expose them to different hazards that affect their health.

Finally, the return home may also play into things. Different family roles lead to different stressors and levels of social support that can influence physical health, Frayne said.

The full research is detailed in the September issue of the Journal of Internal Medicine.